The extra lead in the corners of the platform were removed for
the painting project (about 20,000 lbs). We left this weight off the
platform and used the tiedowns to pull the platform back to a level
position. This gave us some more pretension in td 12 and td 4.

465 (and counting) points were used for the model.

The model data was taken with model15B installed.

The data was taken with heiles calibration scans.

Data was taken 13dec07 thru 16dec07.

A few evenings had some rain. I removed source patterns where the
distomats were not working.

Data was also taken during the day on 15dec and 16dec07. I
removed some sources where the tiedowns had gone slack.

There may still be some errors from loose tension.. The
distomats only read the height once every 2 minutes. When tension comes
back in may take a few minutes to get the platform back where it
belongs.

On 16dec07 evening i installed the model for sband narrow and
started the verification.

The data
used to compute model 17 (.ps) (.pdf)
was taken using model 15 (the previous model). Figures 1-5 show
these
errors. Figures 6 and 7 remove the model 15 correction and show the raw
telescope pointing error. All errors are great circle arc seconds.

Fig. 1 is the azimuth/zenith angle coverage for the input data.

Fig. 2 is the pointing error (za error top, az error bottom)
plotted
versus
azimuth. This is relative to model 15. The left half of each plot is
the
northern portion of the dish (southern sources with declination <
18.2
degrees). The right half of each plot is the southern portion of the
dish
(northern sources).

Figure 3 is the pointing error (za error top, az error bottom)
versus
zenith
angle for the input data relative to the previous model. There is no
linear ramp in za error vs az. It looks like there may be a slight ramp
in az error vs za (i think we are missing a few compressors on the
dome).

Figure 4 is the za and azimuth errors plotted by source order.
The
sources
are color coded.

Fig. 5 is the magnitude and direction of these errors
plotted
versus
azimuth and za. 1 tick mark is 5 arc seconds. At the bottom is a table
of the average magnitude and rms for the entire dish and computed for
every
5 degrees in za.

Fig. 6 has the raw az, za errors plotted versus azimuth. The
model 15
correction
has been removed. Model 17 will be fit to this data set. Fits to 1az,
2az,
and 3az have been over plotted with the amplitude and phase angle of
the
maximum.

The model is fit to the raw errors. An encoder table
spaced every .5 degrees in za is computed for azimuth and zenith angle
errors and then removed. The final residuals are great circle
errors.
The telescope must move in that direction from the computed position to
point at the source. The model 17
fit with residuals (.ps) (.pdf)
are:

za residuals

az residuals

total residuals [asecs]

mod17 noEncTable

6.30

8.27

10.4

mod 17 with Enc Table

4.39

2.99

5.31

Fig. 1 plots the residuals versus za for the azimuth and za
errors. The
encoder table has not yet been removed. The computed encoder
table
is over plotted in red.

Fig. 3 plots the azimuth and za (raw Errors - (model + encoder
table)
residuals
versus azimuth. There is more scatter in the azimuth residuals that the
za. The tilt sensor measurements show a 6az term over part of the
dish. The encoder rack gear for the azimuth also has some runout. It
will
cause a azimuth scatter (with a za dependence since these are great
circle
errors).

Fig. 6 has the residual error plotted versus azimuth and zenith
angle.
1 tick mark is 5 arc seconds. A table of the average error and the
errors
every 5 degrees za is at the bottom of the plot. Also included is the
model
parameters and values.

Fig 1 has the model residuals removing one source at a time. 0 is
J1504+104,
1=J2123+055.. to 27=J0038+124. The black line is the total rms
residuals
while the red it the azimuth and the green is the zenith angle. The top
plot does not include the encoder table while the bottom plot includes
it. Removing the 11th source J1924+334 makes the largest
improvement
in the model. The previous model also had the largest error for the 33
deg Dec source. This source was taken in the afternoon so there may
have been a problem with the tiedown tensions at the start..

Figure 2 plots the mean pointing error and its rms for each
source
track
that was not included in the model. The model was evaluated without
source
i, then the mean and rms of the pointing model along the az,za track
for
source i was computed.

An azimuth encoder table for azimuth residuals was
built
by smoothing the great circle azimuth residuals in azimuth and then
removing
this from the (model-zaEncTbl) azimuth residuals. I first tried
smoothing
the little circle errors (azErr/sinza) thinking that the azimuth
encoder wrack gear was the largest culprit and it should give a little
circle error. The residuals didn't get much better. The low za errors
were
messing up the averages. This must mean that the azimuth residual
errors
are great circle and not little circle.
The table step has 1 degree steps in azimuth.
Different
az smoothing was tried. The az
encoder table results (.ps) (.pdf)
are shown in the figure: (the azimuth encoder table has not been
installed).

Fig 1 top is the azimuth encoder table made by smoothing to 1
through 6
degrees azimuth (bottom to top).

Fig 1 bottom plots the azimuth encoder residuals (black line) for
azimuth
smoothing 1 through 19 degrees. The green line is the azimuth residuals
without the azimuth encoder table. The red line is the total residuals
(za plus az) for the various smoothing.

Fig 2 over plots the azimuth residuals and the az enctable
smoothed to
3 and 6 degrees azimuth.

Fig3 is a fourier transform of the azimuth encoder table (built
with 1
degree smoothing). The top plot is plotted versus cycles and the bottom
plot versus period (in degrees). The power is at 4 cycles and 12 cycles
(90 degree spacing and 30 degree spacing). (I think the az encoder rack
gear has 15 degree sections...see
az rack gear)

The model includes constant terms (great circle) in azimuth and zenith
angle for each receiver. These terms can differ receiver to receiver
because
of positioning error of the horn on the rotary floor. The model is made
with sband narrow. After the model we need to compute what the constant
offsets for the other receivers are (ideally it would remain constant).

On 16dec07 5 sources were tracked with sbn
and
the
new model 17 installed. The sources were:

Some of these sources were then retracked with the other receivers
to measure the receiver constant az,za values from the sbn model.
Before each receiver was used, an offset was included to get the
receiver
close to where it was supposed to be.

16dec07: sbn tracking

18dec07: lbw,cb tracking. two cb source offsets don't agree. One
was J0659+082. May need to redo it with a different src.

18dec07:430, 19dec07 xb.. data taken with old model, ignore

21dec07: 430,327 taken with old model.. ignore

12jan08: xb only 10 patterns on J0141+138

16jan08: xb 4 patterns J0659+082

17jan08: 430 using B0949+287. Td 12 was not
working so ignore data.

The plots
show the tracking error for sbn and the other receivers. (.ps)
(.pdf).
The first 9 plots show the sbn error and the other receiver error
(one per page). Black is the sbn measurement. Red, green, blue, purple
are the up to 4 frequency bands of the "other" receiver. The left
column
has azimuth errors while the right column is za errors. The
numbers
printed are the mean(sbnErr) - mean(rcvrErr) in arcseconds. The figures
are:

327 Mhz. 3 frequency bands,

430 Mhz . 3 frequency bands ,

610 Mhz . 3 frequency bands,

lbw. 4 frequencies, 2sources.

sbw.

sbh.

cband. 4 frequencies, 2 sources. may want to redo one.

cbandHi.

xband. 4 frequencies, 1 partial source.

Mean(sbn)-mean(rcv) for each source and frequency band. black is
the
azimuth
error and red is the za error.

Ideally the (sbn-rcv) value should be the same for
all
sources and frequencies of a receiver.
The offsets for the individual receivers as
calculated
from the above data is shown in the table below.

A variogram
of the raw errors and pointing residuals (.ps) (.pdf)
shows the correlation of the measurements versus separation of the
points.
The residual error and raw pointing error difference is computed for
all
points on a pair wise basis. A metric is then defined for the point
separation
and is used to bin the data. The variance of the pair differences for
each
bin is then computed and plotted versus the distance. For each figure
the
top plot is the pair wise difference of the pointing residuals
(including
the zaencoder table) while the bottom plot has the pair wise difference
of the raw errors input to make the model.
This data can be used to interpolate the residuals
onto an az,za grid (it gives the nugget (y intercept), range (where the
variance increases), and the sill (value where the variance
levels
off) for the krigging routine)

Fig. 1 is the variogram using the great circle angular separation
of
the
points as the metric. The separation was binned to .3 degrees steps.
The
za correlation increases until za=2. degrees and then levels off.
The az residuals variance increases till about 5 degrees. The 25 foot
spacing
of the north south main cables is about 1.6 degrees (1.5 degrees is
close
to the 25 foot spacing of the main cables ). The large correlation in
the
bottom plot is the 1az term of the raw pointing errors.

Fig. 2 projects the points into the xy plane and then measures the
distance (since the kriging would be done in this plane). It looks the
same as that of figure 1.
processing: x101/model/dec07/doall.pro